1. Fields of the Invention
This invention relates generally to a portable electric circular saw, and more particularly to an electric circular saw of the type capable of adjusting the angle of the cut.
2. Description of the prior art
A typical prior portable electric circular saw of the above type is shown in FIGS. 1 through 3 and comprises a housing 1 for accommodating an electric motor therein, a handle 2 projected upwardly from the housing 1, a circular saw blade 3 operatively connected through gearing to a motor shaft, a safety guard 4 fixed to the housing 1 so as to enclose the upper portion of the saw blade 3, and a base plate 5 upon which the above parts are supported and which is adapted to engage the upper surface of a workpiece to be sawed. An adjusting bracket 6 is attached to the front end of the safety guard 4 for connecting the base plate 5 to the housing 1 and at the same time for tiltably supporting the housing 1 upon the base plate 5 so that the saw blade 3 can be set at an angle in order to make a beveled or angle cut across the workpiece to be sawed. To this end, the base plate 5 is pivotally secured by means of a pivot pin 7 to the lower portion of the adjusting bracket 6 so as to be movable about an axis within the plane of the saw blade 3 for effecting the angle cut. The adjusting bracket 6 is provided with a laterally extending lug portion 6a carrying a screw 8 rotatively fixed thereto. Cooperative with and positioned in face to face contact with the lug portion 6a is a generally triangular plate section 5a of the base plate 5 having therein a graduated arcuate slot 9 through which said screw 8 extends. Within the arcuate path of the slot 9 the screw 8 is allowed to move so that the base plate 5 pivots about the pivot pin 7 for adjusting the angle of the saw blade 3 relative to the base plate 5. After the saw blade 3 is set at a desired angle, a wing nut 10 is tightened on the screw 8 to securely fasten the base plate 5 to the housing 1.
However, in this prior art device in which the base plate 5 is directly connected to the safety guard 4, the safety guard 4 should be of substantial mechanical strength for securely supporting the base plate 5 and be therefore made of steel or the like rigid material which adds an extra weight to the device, militating against the demand for reducing the weight of the device to be completely portable and easy to handle. This is particularly disadvantageous where the device is powered by an incorporated electric battery of heavy construction in its nature. In fact, the safety guard 4 should have a still increased strength and weight if the housing 1 includes the battery together with the motor both of heavy construction. Accordingly, the above connecting structure of the base plate 5 and the safety guard 4 has long been a trouble in making the device light in weight enough to be portable. In addition, the above structure in which the base plate 5 is securely fastened to the adjusting bracket 6 at the portion which is laterally spaced considerably from the connecting portion of the adjusting bracket 6 with the safety guard 4 brings about a problem that the torsion force acting about the connecting portion of the adjusting bracket 6 with the safety guard 4 will increase as the connection between the base plate 5 and the lug portion 6a goes far from the pivot pin 7 for attaining easy adjustment of the angle of the cut.